Means for preventing the overwinding of hoist-chains of cranes.



PATENTED MAR. 17, 1903.

I G. MITCHELL. I MEANS FOR PREVENTING THE OVERWINDI NG 0F HOIST CHAINS 0F GRANES.

APPLIOATIOH FILED JULY 3, 1902.

[N VEJV T OR 15718 :0. momumq WASHING UNITED STATES PATENT OFFICE,

GEORGE MITCHELL, OF NACO, ARIZONA TERRITORY.

MEANS FOR PREVENTING THE OVERWINDING OF tlOlST-CHAINS OF CRANES.

SPECIFICATION forming part of Letters Patent N 0. 722,867, dated March 17, 1903. Applicationifiled July 3, 1902. Serial No. 114,279. (Na model.)

Be it known that I, GEORGE MITCHELL, t

means for cutting out the main hoist-motor when through negligence or any other cause the main chain-hoist block reaches the limit of its upward movement, thus preventing injury to the apparatus and possible danger to the workmen that would necessarily result from overwinding of the main hoist-chain.

With these ends in view myinvention consists in a hoisting-drum, its motor, and a chain block or sheave combined with an elec-v tric circuit including the motor and means controlled by said sheave or block for automatically opening the motor-circuit when the sheave or block rises to a predetermined height.

My invention further consists in certain details in the construction, as will be more fully described, and pointed out in the claims.

While my improvement is designed for use on any type of hoisting apparatus wherein the hoisting-drum is actuated by an electric motor, it is particularly applicable for use on overhead traveling cranes.

In the accompanying drawings, Figure 1 is a view of an overhead trolley for a traveling crane embodying my invention; and Fig. 2 is a diagrammatic view of the motor, its circuit, and the contact-arms.

1 represents a. trolley of any construction, carrying a winding-drum 2,to which the hoistchain 3 is attached. This chain carries the pulley-block 4, to which the carrying-hook 5 is swiveled.

The motor 6, which operates the windingdrum 2, is preferably included in a multiplearc circuit 7 between the main leads 8 8 from a suitable generator. block or sheave 4: from rising high enough to engage the winding-drum, and thus endanger the apparatus, it is desirable that the motor 6 shall be stopped automatically before the sheave reaches the winding-drum, and in order to insure this I prefer to provide means whereby the motor-circuit-shall be opened and the motor thus disabled. This can be readily accomplished by placing a fuse 9 in the multiple-arc branch in series with the motor, so that by short-circuiting the motor the multiple-arc motor-circuit will be opened by the blowing of the fuse. For the purpose of thus shortcircuiting the motor when the block or sheave 4t rises to a predetermined height I provide the trolley l with contact- .motor and the fuse-box, or said conductors may be connected directly with the motor-terminals. From this construction it will be seen that when the block or sheave 4 rises sufficiently high to enter between and electrically connect the contact-arms 1O 10 the motorwill be short-circuited and the consequent sudden rise of current in the multiplearc motor-circuit will blow the fuse 9, and thus open themotor-circuit.

Having fully described my invention, what I claim as new, and desire to secure by Letters Patent, is-

, 1. The combination with a winding-drum and a sheave to be raised thereby, of an electric motor for operating said drum, an electric circuit including the motor, and electrically-operated means controlled by said sheave for automatically opening the motor-circuit when the sheave rises to a predetermined height.

2. The combination with a Winding-drum,

and a sheave to be raised thereby, of an electric motor for operating the winding-drum, an electric circuit including said motor, a fuse in said circuit, and means controlled by the sheave for causing said fuse to be blown when the sheave rises to a predetermined height.

3. The combination with a winding-drum In order to prevent the and a sheave to be raised thereby, of an electric motor for operating said drum, a multiple-arc circuit including said motor, a fuse in series with the motor in said multiple-arc circuit, contact-arms arranged to receive the sheave between them, and conductors connecting said contact-arms with the multiplearc circuit at respective sides of the motor.

4:. The combination with a winding-drum and a device to be raised thereby, of an electric motor for operating the drum, an electric circuit including the motor, and electricallyoperated means controlled by said device for automatically opening the motorcircuit when the device rises to a predetermined I5 height.

In testimony whereof I have signed this specification in the presence of two subscribi112 witnesses.

GEORGE MITCHELL.

Witnesses: I

S. G. NOTTINGHAM, A. W. BRIGHT. 

